Data Validation
 

I am using data validation to prompt users to select from a drop down list.
I have done these several times before, but I have a file with several sheets
and can successfully do this on all sheets except one. The validation and
error message works but the drop down list is not visible. I have checked
the cell format, tried copying a pasting a successfuly one from another sheet
without any joy. I can even copying the cell from this sheet into another
one and the the dropdown is visible!
Any ideas??
Thanks
Duncan